Traditional liner cementing involves delivery of cement through a liner that is hung off casing with the cement going through a cement shoe at the lower end of the liner and back around in the annular space around the suspended liner. Fluid is displaced by the advancing cement through the liner hanger. At the time of fluid displacement with cement, the seal on the liner hanger is not set and there are gaps between the anchor slips through which the displaced fluid moves. After the cement is delivered a trailing wiper plug is released to clear the liner of excess cement. The liner shoe has a check valve to prevent return of the cement. The seal on the liner top packer is then set and the liner running tool is pulled out of the hole. The shoe can be milled or drilled out and more hole can then be drilled and the process can be repeated.
In some situations there can be doubt that the cement is adequately distributed using this method and an alternative technique for cement placement is desired. This is particularly beneficial when a formation is particularly weak which can result in significant fluid loses due to low fracture gradients.
Cementing bottom up and then top down presents a challenge when the liner hanger/packer is designed such that the slips and packing element are set simultaneously. This simultaneously set hanger/packer cannot be set until the top down cementing is over. To accomplish the sequence of bottom up and then top down the ports for top down cementing have to be closed for initial displacement of the bottom up cement job, then opened for the top down cement job and finally reclosed so that pressure can be applied to set the liner hanger/packer. This operation can entail, in one instance, waiting for a ball to drop to a seat to close a cementing port and then further object displacement to close off the running string at the liner hanger/packer so that pressure can be applied to set the liner hanger/packer. The running tool still needs to be released from the liner hanger packer after the set so time is of the essence to be sure the running tool can still be released after setting the liner hanger/packer with cement potentially surrounding the tools. The most significant and feared non-productive time event in running liners is generally considered to be cementing running tools in the hole. For that reason, techniques are presented that shorten the time from the conclusion of the top down cementing to the setting of the liner hanger/packer and release of the running tool from the set liner hanger/packer. Those skilled in the art will appreciate these and additional aspects of the present invention from a review of the description of the preferred embodiments and the associated drawings while recognizing that the full scope of the invention is to be found in the appended claims.